GB2532973A

GB2532973A - Lead-on ramp

Info

Publication number: GB2532973A
Application number: GB1421492.8A
Authority: GB
Inventors: Hayes Anthony
Original assignee: Marmon Group Ltd
Current assignee: Marmon Group Ltd
Priority date: 2014-12-03
Filing date: 2014-12-03
Publication date: 2016-06-08
Also published as: GB201421492D0

Abstract

A lead-on ramp 10 for attachment to a chassis (12, Figure 3) of a tractor unit (14, Figure 3) has a lower ramp end 18 and an upper ramp end 20, between which extends a ramp surface 16. Lead-on ramp 10 further has means 26 for mounting ramp 10 to chassis 12 and a region of localised weakness about which ramp 10 is biased to deform. The region of localised weakness may be a substantially linear region, for example a row of apertures 28 and/or a notch 30. Ramp 10 may deform about the region of localised weakness when subjected to certain impacts so as to prevent or minimise damage to the tractor unit. Ramp 10 may be of T-shaped or L-shaped cross-section and may be formed from 8 mm thick steel plate.

Description

Lead-on ramp

TECHNICAL FIELD

The invention relates to a lead-on ramp for attachment to a chassis of a tractor unit.

BACKGROUND

Lead-on ramps (also referred to as pick-up ramps and run-up ramps) are commonly provided on a tractor unit, i.e. a towing vehicle, to facilitate its coupling with a trailer. Typically, lead-on ramps are a pair of spaced apart metal rails which are rigidly attached to a chassis of the tractor unit and slope upwards from the rear of the tractor toward a fifth wheel plate on the tractor unit. When coupling a tractor unit with a trailer, the lead-on ramps may guide the front end of the trailer upwards in order to bring a kingpin provided on the trailer into approximate vertical alignment with the fifth wheel. During a coupling operation the ramps also stop the trailer being forced against or dropped on rear mudguards/mud wings provided on the tractor unit. The mudguards/mud wings may be expensive to replace or repair.

The profile of each lead-on ramp must allow for articulation in the vertical and horizontal directions between the tractor unit and the trailer when the two are coupled.

For example, a predetermined vertical articulation angle of ±6° degrees may be allowed for. However, when the predetermined angle is exceeded a front under body area of the trailer may clash with one or both of the lead-on ramps. Although a clash is a rare occurrence, there is an increased likelihood of a clash when vertical articulation between the tractor unit and the trailer coincides with horizontal articulation, for example when the tractor unit is making a turn while travelling over a hump or boarding a ferry. A clash may result in significant damage to the chassis and/or the mudguards/mud wings of the tractor unit and can also damage the front underbody area of the trailer. Damage to the chassis removes the tractor unit from service to allow for repairs to be made, as well as being expensive to repair.

It is an object the invention to mitigate at least some of the aforesaid problems associated with currently known lead-on ramp arrangements.

SUMMARY OF THE INVENTION

According to the invention a lead-on ramp is provided for attachment to a chassis of a tractor unit, the lead-on ramp having a lower ramp end and an upper ramp end, a ramp surface extending between the ramp ends, means for mounting the ramp to the chassis, and a region of localised weakness about which the ramp is biased to deform.

Accordingly, the ramp of the invention may deform about the region of localised weakness when subjected to certain impacts thereby preventing or minimising damage to the tractor unit.

The ramp surface may be provided as a flange supported by a web, the web being provided with the means for mounting the ramp to the chassis. The region of localised weakness may be provided at least in part by one or more apertures formed in the web. One or more apertures in the web reduce the cross-sectional area of the web over the region of localised weakness. Further, the region of localised weakness may be provided at least in part by one or more notches formed in the flange. One or more notches in the flange reduce lateral restraint provided by the flange.

The region of localised weakness is conveniently provided between the upper ramp end and the means for mounting the ramp to the chassis. Further, the region of localised weakness is conveniently a substantially linear region which extends across the ramp between the upper ramp end and the means for mounting the ramp to the chassis. Moreover, in preferred practical embodiments the region of localised weakness extends across the ramp surface between the upper ramp end and the lower ramp end at a location which is closer to the upper ramp end than the lower ramp end.

A further aspect of the invention is a tractor unit having a coupling for attachment of a trailer, the tractor unit comprising a pair of spaced apart lead-on ramps configured as just outlined. These lead-on ramps may prevent damage to the tractor unit by preferentially bending in the event of impact between the trailer and said lead-on ramps.

BRIEF DESCRIPTION OF THE DRAWINGS

A practical embodiment of the invention will now be described by way of example only, with reference to the accompanying figures, in which: Figure 1 is a perspective view of an embodiment of a lead-on ramp in accordance with the invention; Figure 2 is a side on view of the lead on ramp shown in Figure 1; and Figure 3 is side view showing the lead-on ramp of Figure 1 attached to a chassis of a tractor unit, i.e. towing vehicle.

DETAILED DESCRIPTION

As shown in figures 1 and 2, an embodiment of a lead-on ramp 10 in accordance with the invention is formed by a web 24 and a flange 22. The flange 22 is supported by the web 24 and provides a ramp surface 16 which slopes upwards between a lower ramp end 18 and an upper ramp end 20. The web 24 is welded to an underside of the flange 22 such that ramp 10 is approximately "T-shaped" in cross-section. Means for mounting the ramp 10 to a chassis 12 of a tractor unit 14, as shown in figure 3, are provided in the form of bolt holes 26 which are formed through the web 24.

The flange 22 and the web 24 are fabricated from 8mm thick steel plate. However, in other embodiments any suitable thickness of plate may be used, for example, within a range of 6-16mm.

The ramp 10 includes a region of localised weakness about which the ramp 10 is biased to deform, particularly if an upper region of the ramp is impacted. In the illustrated embodiment, the region of weakness is provided in part by a row of apertures 28 formed in the web 24 and in part by two notches 30 which are formed in the flange 22. The apertures 28 comprise four circular holes which are spaced apart along a line extending obliquely across the web 24 as well as a recess aligned with those holes at the front edge of the web 24. The presence of the apertures 28 reduces the cross-sectional area of the web 24. This reduction in the cross-sectional area reduces the stiffness of web 24 over said linear region making it the region of weakness, about which the web 24 will tend to deform.

The flange 22 provides lateral restraint to the ramp 10, i.e. the flange 22 increases the resistance of the ramp 10 to bending and lateral torsional buckling. Introduction of the notches 30 to the flange 22, particularly in the illustrated configuration where they are located to oppose each other by being cut in from directly opposing locations on the flange edges, removes much of the effect of lateral restraint and consequently extends the localised weakness through the flange 22.

The region of localised weakness formed by the apertures 28 and the notches 30 is a substantially linear region transecting the ramp 10, i.e. the region of weakness forms a line extending across the ramp 10. As illustrated, the region of weakness is formed in the ramp 10 at a positon between the ramp ends 18, 20, which is somewhat closer to the upper end 20 than the lower end 18, and between the upper ramp end 20 and the bolt holes 22. Of course, it will be understood that in other embodiments the exact position of the localised weakness may be different.

In use, a pair of such lead-on ramps 10 are attached to the chassis 12 of a tractor unit 14, as shown in figure 3. They are positioned in conventional manner, in a generally side-by-side spaced apart arrangement, one adjacent each side of the chassis 12. The tractor unit 14 is a towing vehicle for towing a trailer and will typically be provided with a fifth wheel coupling (not shown) for attachment of a trailer (also not shown). In some embodiments, the pair of ramps 10 may be connected by a crosspiece. The tractor unit 14 also has a mudguard (sometimes referred to as a mud wing) 32 associated with each wheel 36. A centreline 34 of the fifth wheel coupling is shown in figure 3.

Each ramp 10 is attached to the chassis 12 adjacent a rear end of the tractor unit 14, to the inner side of the respective mudguard 32, such that the ramp surface 16 extends upwards from the rear end of the tractor unit 14 in the direction of the fifth wheel coupling. The positon of the two ramps 10 on the chassis 12, particularly the trajectory of the respective ramp surfaces 16 and the location of the upper ends 20 thereof, prevents the mudguards 32 from making contact with the trailer during a coupling or uncoupling operation. This is because the ramp surface 16 is inclined as a guide surface for the trailer and is set to project higher than the mudguard 32 relative the chassis 12.

During coupling of the tractor unit 14 to a stationary trailer, the ramp 10 may guide a front end of the trailer upwards to a level where the fifth wheel coupling is approximately in vertical alignment with a kingpin on a front underbody area of the trailer. When being coupled to the tractor unit 14, the trailer may contact the ramp 10 such that the weight of the trailer applies a load to the ramp 10 in the plane of the web 24. Under typical service conditions the ramp 10 will resist a load applied in the plane of the web 24 without deformation.

The fifth wheel coupling enables articulation in both the vertical and the horizontal direction between the tractor unit 14 and the trailer when the two are coupled. Vertical articulation is necessary in order to allow for the articulated vehicle travelling through the beginning or end of an incline. Transport regulations typically specify an angle of vertical articulation a between the tractor unit 14 and the trailer of ±6°. The vertical clearance between the front underbody area of the trailer and the upper surface of the fifth wheel and of the chassis on which it is mounted is typically kept to an absolute minimum in order to maximise the storage capacity of the trailer. Consequently, the upper end 20 of the ramp 10 tends to lie just below the 6° angle, as shown in figure 3. On occasion, the ramp 10 may impact the front under body area of the trailer if articulation in the vertical direction exceeds the allowable angle.

While such an impact or clash is a rare occurrence, there is an increased likelihood of a clash when vertical articulation occurs at the same time as horizontal articulation. A clash may occur, for example, when the tractor unit 14 performs a turn while towing the trailer onto or from a ferry ramp or over a hump in the road, such as a hump back bridge. When a clash does occur, the weight of the trailer may apply an acentric load to the ramp 10, i.e. a force may be applied to the ramp 10 which is not applied in the plane of the web 24. Consequently, the ramp 10 may act as a lever arm about the means for rigidly mounting the ramp 10 to the chassis 12. This could transfer a bending moment into the chassis 12 which could result in significant damage to the tractor unit 14. The region of localised weakness extends across the lever arm formed by the ramp so as to bias the ramp 10 to deform, e.g. bend, and prevent a bending moment being transferred into the chassis 12. As such, the ramp 10 is sacrificial so as to prevent or minimise damage being sustained by the tractor unit 14 or the mudguard 32.

S

Further, by sacrificing the ramp 10 in the event of a clash, damage to the front underbody area may be minimised or avoided.

Of course, in the event that a significant load is applied to ramp, whether or not in the plane of the web 24, the ramp 10 may deform, e.g. through lateral torsional buckling. If the lead-on ramp 10 becomes deformed it can be removed from the chassis 12 and a replacement ramp installed.

In any embodiment, the invention provides a lead-on ramp which is biased to deform about a region of localised weakness. However, the invention is not restricted to the details of the forgoing embodiment and other embodiments are possible within the scope of the invention as defined in the claims. While four circular apertures and one semi-circular aperture are shown in the illustrated embodiment, in alternative embodiments any suitable number of apertures may be used. Further, the apertures may be of any suitable size and shape, for example one or more elongate apertures may be formed in the web to provide the region of localised weakness. The web may be configured in any suitable manner for attaching the ramp to the chassis, for example the web may include elongate slots in the place of the bolt holes. The use of elongate slots provides an amount of play between the ramp and chassis when the attaching the ramp.

In certain embodiments it may be preferable that apertures are not provided in the web and that only one or more notches are provided in the flange. Alternatively, in embodiments where plural apertures are provided in the web, it may not be necessary to provide notches in the flange. Further, the ramp may not have a "T-shaped" cross-section and instead may have a flange which extends unequally on either side of a web. In certain embodiments, the ramp may have an "L-shaped' cross-section or may be in the form of a downwardly open channel section.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to', and they are not intended to (and do not) exclude other components. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Claims

BCLAIMS1. A lead-on ramp for attachment to a chassis of a tractor unit, the lead-on ramp having a lower ramp end and an upper ramp end, a ramp surface extending between the ramp ends, means for mounting the ramp to the chassis, and a region of localised weakness about which the ramp is biased to deform.
2. A lead-on ramp according to claim 1, wherein the ramp surface is provided as a flange supported by a web, the web provided with the means for mounting the ramp to the chassis.
3. A lead-on ramp according to claim 2, wherein the region of localised weakness is provided at least in part by one or more apertures formed in the web.
4. A lead-on ramp according to claim 2 or 3, wherein the region of localised weakness is provided at least in part by one or more notches formed in the flange.
5. A lead-on ramp according to any preceding claim, wherein the region of localised weakness is provided between the upper ramp end and the means for mounting the ramp to the chassis.
6. A lead-on ramp according to any preceding claim, wherein the region of localised weakness is a substantially linear region which extends across the ramp between the upper ramp end and the means for mounting the ramp to the chassis.
7. A lead-on ramp according to any preceding claim, wherein the region of localised weakness extends across the ramp surface between the upper ramp end and the lower ramp end at a location which is closer to the upper ramp end than the lower ramp end.
8. A tractor unit with a coupling for attachment of a trailer, the tractor unit comprising a pair of spaced apart lead-on ramps according to any preceding claim.
9. A lead-on ramp substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.